Very, very true. All defenses need to in layers to buy time. I am impressed with the security in apartment buildings in my visits to eastern europe: 1) punch in code or intercom to enter building to the stairwell/elevator; 2) at the floor you want, another locked door to get to the wing of the apartment you want, again intercom or you know the code, and 3) get past the locked apartment door.

Yet, my niece had to call the police when some guys made it to her front door and were heard to be working on getting in and making comments like "she is in there, lets get her. . ."

The police got there in time, but just so, thus, from that point of view the system worked. But her last passive defense was about to be breached. So, to be frank, I would have liked her to have that last resort, an active defense. Not permitted where she lives.

I am also personally familiar with a woman here in the U.S. who was on the phone with with 911 trying to get help as a man was breaking into her room. Regretfully, the police arrived too late to save her from assault and murder. A last resort solution is sometimes necessary.